WO 00/011473 describes methods of electrochemical analysis of an analyte (e.g antigen) in complex samples by using potentiometric sensor electrodes for electrochemical detection of the analyte. The sensor electrodes for use in these methods generally comprises an electrically conductive electrode coated with an electroconductive polymer (e.g. polypyrrole). Receptor molecules capable of selectively binding to the analyte to be detected are immobilised in or adsorbed to the electroconductive polymer to enable the detection of the desired analyte. Detection is achieved via formation of a specific complex, containing the analyte and also a label component which facilitates electrochemical detection, bound to the receptor molecule at the surface of the sensor electrode.
The detection methods of WO 00/011473 generally comprise a number of steps summarised as follows:    (a) providing a sensor electrode having an electroconductive polymer coating an having immobilised or adsorbed receptors specific for the analyte of interest;    (b) treating the sensor electrode by immersion in a sample so that said desired analyte binds to the immobilised or adsorbed receptors at the sensor surface to form a complex which also includes a label component;    (c) removing the sensor electrode from the sample and subsequently monitoring the electric potential difference between the treated sensor electrode and a reference electrode when both are immersed in a suitable inactive measuring buffer, and subsequently;    (d) monitoring the electric potential difference between the sensor electrode and a reference electrode following exposure to another buffer, but one that is electrochemically active, thus promoting electrochemical activity of the label component.
WO 03/019171 describes improved methods for the production of potentiometric sensor electrodes and also improved methods of electrochemical detection using these sensor electrodes. However, the improved methods of electrochemical detection described in WO 03/019171 still rely on a first measurement of electric potential difference between the treated sensor electrode and a reference electrode when both are immersed in a suitable inactive measuring buffer, and subsequent monitoring of the electric potential difference between the sensor electrode and a reference electrode following exposure to another buffer which promotes electrochemical activity of the label component.
The present inventors have how developed a simplified method of electrochemical detection which does not require a separate step of measuring the electric potential difference between the treated sensor electrode and a reference electrode when both are immersed in an inactive measuring buffer, prior to exposure to a buffer which promotes electrochemical activity of the label component, to be carried out each time the method is used for detection of a given analyte.